Method of forming a tube joint

ABSTRACT

A constrictor ring and tube joint formed thereby in which the constrictor ring is provided with a tapered bore and which is also tapered externally in such a manner that the end having the smaller internal diameter also has the greater external diameter. The constrictor ring is internally dimensioned to be partially received on a collar or coupling connecting the ends of two tubes placed in abutment or the enlarged or bell end of a tube which receives the plain end of a mating tube and then is forced over the collar or bell end to cause local annular compression of the collar or bell end sufficiently to cause corresponding annular compression of the tube within and produce a high strength fluid tight tube joint.

This is a division of application Ser. No. 266,055, filed June 26, 1972,now U.S. Pat. No. 3,827,727, which is a contnuation of application Ser.No. 876,682 filed Nov. 14, 1969 and now abandoned.

SUMMARY OF THE INVENTION

The present invention is directed to a constrictor ring and tube jointformed thereby and is summarized in the following objects:

First, to provide a constrictor ring and tube joint which, when theconstrictor ring is applied to a collar which receives a pair of tubeends in abutment, or when applied to the bell end of a tube whichreceives the plain end of a mating tube, effects local annularcompression to the extent a seal as well as a mechanical bond is formedproducing a dependable tube joint.

Second, to provide a constrictor ring and tube joint wherein theelements of the tube joint require no special preparation and assemblyis completed by forcing the constrictor ring axially onto the joint.

Third, to provide a constrictor ring and tube joint wherein theconstrictor ring is tapered both internally and, if desired, externallyin such a manner that the radial thickness increases in proportion tothe local hoop stress applied to the constrictor ring.

Fourth, to provide a constrictor ring of the type indicated in thepreceding objects which may include an annular skirt extending axiallyfrom the larger end of the ring and tapered internally to compress anextremity of the tube joint into mutual engagement.

Fifth, to provide a constrictor ring which incorporates a lockingshoulder adapted to resist removal of the locking ring once it has beeninstalled.

Sixth, to provide a constrictor ring and tube joint which, whileparticularly adapted for direct bond between the elements of the joint,may be arranged for the introduction of solder, various epoxys or othersealing and bonding means.

Seventh, to provide a constrictor ring and tube joint, an embodiment ofwhich is particularly adapted for the joining of an essentiallynon-deformable tube to a similar tube or to other apparatus by use of adeformable collar or sleeve which interlocks into grooves formed in thenon-deformable tube.

Eighth, to provide a constrictor ring and tube joint wherein theconstrictor ring is provided with a sleeve to guide the constrictor ringinto place even though only part of the end of the guide ring isavailable for receiving axial force, thereby providing a constructionwhich is particularly adapted for securing U-tubes to the ends ofcondenser or heat exchanger tubes.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a tube joint, utilizing a collar or sleeve,showing one constrictor ring in position and one constrictor ring priorto being moved into position.

FIG. 2 is a similar plan view of a modified form of tube joint, in whichone tube is provided with a bell end, the constrictor ring being shownin position.

FIG. 3 is another plan view, showing a modified form of the constrictorring.

FIG. 4 is an enlarged fragmentary sectional view, taken through 4--4 ofFIG. 1.

FIG. 5 is an enlarged fragmentary sectional view, taken through 5--5 ofFIG. 2.

FIG. 6 is a fragmentary sectional view, taken through 6--6 of FIG. 3,showing a modified form of the collar.

FIG. 7 is a fragmentary sectional view, corresponding to FIG. 4, butshowing a modified form of a collar.

FIG. 8 is an enlarged sectional view, showing a modified form ofconstrictor ring.

FIG. 9 is an enlarged fragmentary sectional view of another modifiedform of constrictor ring.

FIG. 10 is an enlarged fragmentary sectional view of a tube jointadapted for connection to an essentially non-deformable tube.

FIG. 11 is an end view of a U-tube and connectors for joining a pair ofcondenser or heat exchanger tubes.

FIG. 12 is a fragmentary side view of the connector shown in FIG. 11.

FIG. 13 is an enlarged fragmentary sectional view, taken through 13--13of FIG. 12.

FIG. 14 is an enlarged fragmentary sectional view, similar to FIG. 13,but showing the construction adapted to a collar connected joint.

The present invention is directed to a constrictor ring tube joint; thatis, a joint intended primarily but not limited to tubing such asaluminum, copper, brass, steel and the like. The invention is alsoprimarily directed to tubing of relatively small size, but may beadapted to tubing of large diameter. In any case, it is essential thatthe tubing or at least the external tube or the coupling be capable ofradial constriction under the forces applied in the course of assembly.

The construction shown in FIGS. 1 and 4 utilizes a pair of tubes 1,which are joined together by a collar 2. Preferably the materialcomprising the tube and collar is the same to avoid electrolytic actionor different thermal expansion. The collar may be slightly greater inwall thickness than the tubing and may be work hardened or otherwisetreated so that its strength or hardness is greater than the tubing. Theends of the tubes received in the collar do not require specialtreatment except to be free of burrs and free of longitudinal scratchesof any appreciable magnitude. The same conditions apply to the collar 2,except small bevels 2a may be provided. The clearance tolerance betweenthe tubes and the collar is such as to accommodate the variation intubing and collar diameters which normally occur.

Each end of the collar 2 receives a constrictor ring 3, which may beformed of the same material as the collar and tube, or if of differentmaterial, may be coated to minimize electrolytic action. The constrictorring 3 includes a conical bore 4, having a larger or leading end 5,provided with a slight bevel and a constricted or trailing end 6,preferably forming a relatively sharp corner.

The outer surface of the constrictor ring 3 includes a conical portion 7and a cylindrical portion 8. The conical portion 7 diverges from theleading end 5 toward the trailing end so that the wall thickness of theconstrictor ring increases toward the trailing end 6. While theconstrictor ring may be cylindrical throughout, the conical portion 7provides some weight reduction as the hoop stress is less at the leadingend. The increase in diameter in the conical portion may be such thatthe hoop stress is uniform. To reduce the force required to press thering on the collar, the ring may be provided with an internal coating ofa lubricant, such as oil or a fluorocarbon. Preferably, however, a drylubricant, such as Molybdenumdisulphide, may be used.

The tube joint, as shown in FIGS. 1 and 4, is assembled as follows:

The tubes 1 are placed in essentially abutting relation midway withinthe collar 2. While the tubes and collar are held in this position, aconstrictor ring 3 is presented to each end of the collar 2, as shown atthe left side of FIG. 4. It will be noted that the leading end of thering 3 is capable of overlapping slightly the corresponding end of thecollar, and that the small or rudimentary bevel 2a may converge towardthe tip of the constrictor ring so that any lubricant which may beapplied is squeezed between the collar and constrictor ring rather thanscraped off. While each constrictor ring may be applied separately byaxial pressure while applying restraining engagement to the opposite endof the collar 2, it is convenient to apply axial pressure simultaneouslyto both constrictor rings.

The internal dimension of the constricted or trailing edge of theconstrictor ring is such that when the ring is forced on the collar, thecollar is compressed radially a sufficient distance not only to pressthe collar against the tubing, but to compress the collar sufficientlythat the tubing underlying the collar is also compressed radially. Asthe constrictor ring is moved on the collar inwardly from the extremitythereof, the protruding extremity tends to spring back slightly, formingessentially an obtuse V-angle 9, and a similar obtuse V-angle 10 isformed in the tube, as shown at the right side of FIG. 4. The amount ofspring back, of course, depends upon the nature of the materialcomprising the tubing and the collar. If a soft aluminum or copper isused, the spring back is minimal. If the material be steel, such asstainless steel, a substantial spring back may occur. In either case,however, a fluid tight seal is formed. Furthermore, tests have shownthat the connection formed between the collar and tube may be such thatif tension is applied to the tube, the tube will fail before theconnection is broken.

The increase in thickness from the leading end 5 to the trailing end 6of the constrictor ring is such that although the radial outward forceat the trailing end 6 substantially exceeds that at the leading end 5,the stress within the constrictor ring need never exceed the elasticlimit of the material forming the constrictor ring. The slight radialexpansion which may occur is well within the elastic limits of thematerial with the result that an elastic force is maintained against thecollar 2 and the tube 1.

Reference is directed to FIGS. 2 and 5. The construction hereillustrated differs only in that a bell end 11 is provided on one tubeso that the bell end may be slipped over the normal end of the othertube. The bell end 11 performs the same function as the collar 2 and isdeformed in a like manner. However, if the plain end of the tube bottomsagainst the inner shoulder 11a at the inner end of the bell 11, thisbearing engagement may serve as a counter bearing for an installationtool, not shown, which bears against the outer shoulder 11b of the bellwhen the constrictor ring is forced into place.

In the forming of a conventional connection between tubing, solder or ameltable bonding agent is often placed in internal grooves provided inthe collar, then, after assembly of the tubes therein, the solder orother bonding agent is heated so as to flow between the collar and tubeand bond thereto. A similar connection may be augmented by theconstrictor ring, as illustrated in FIG. 7, in which the collar 2 isprovided with an internal groove 12 inwardly from each end, in which isinitially placed a ring of solder or other bonding agent 13. When theinitial ring of bonding agent is heated, the bonding agent isdistributed between the collar and tube, as indicated by 14. Little ornone of the bonding agent will flow between the constricted portions ofthe collar and tube due to the tight fit therebetween. If the collar andtubes are assembled and heated to distribute a bonding agent beforeapplication of the constrictor ring, an intervening coating, not shown,will occur between the constricted portions of the collar and tube.

Reference is directed to FIGS. 3 and 6. The construction here shown isessentially the same as that shown in FIG. 5, except that theconstrictor ring 3 is provided with a tail ring 15, having a leading end16 joined to the trailing end of the constrictor ring and formingtherewith an internal shoulder 17. The trail ring has a conical bore 18,preferably sloping at a lesser angle than the bore 4 of the constrictorring, and forming a trailing end 19 of lesser diameter than the leadingend 16. The taper of the bore 18 may be merely enough to press thereceiving end of the bell 11 tightly against the tubing although slightradial compression preload may occur. The trail ring provides aredundant seal and relieves the mail seal at 10 from the influence ofexternal forces such as bending or vibration forces. More particularly,the bearing engagement between the extremity of the bell 11 and the tubetherein in the plane of the trailing end 19 and the bearing engagementbetween the shoulder 11a and the extremity of the inner tube tend toreduce the effect of external loads in the main seal area 10.

Reference is now directed to FIG. 8 which illustrates a modification ofthe constrictor ring particularly suited for tubing of large diameter.The constrictor ring 21, here illustrated, is essentially threeconstrictor rings 3 joined end-to-end forming three beveled portions 4a,a leading end or portion 5a and three trailing ends or shoulders 6a.When applied to a collar, the operation of each portion is essentiallythe same as the previously described constrictor ring 3. While threeportions are shown, two or four, or more, portions may be provided.

Reference is now directed to FIG. 9, which shows another modification ofthe constrictor ring. In this construction, the constrictor ring 3 isprovided with an axial extension 22 at its trailing edge which clearsthe collar 2 or the bell end 11, and terminates in an internal flange23, dimensioned to clear the inner tube. The flange forms a stop whichlimits the distance that the constrictor ring may be forced over thecollar or outer tube.

Reference is now directed to FIG. 10. This construction is intendedprimarily for a tube 24, which is essentially non-deformable; forexample, a tube formed of high strength alloys or a tube containingrefractory material. The tube 24 is provided with a tapered end 25 and aseries of shallow annular channels 26. A collar 2 is utilized; however,it is essential that the collar be formed of realtively yieldablematerial. Also, it is preferred to use a constrictor ring, similar tothe constrictor ring 21. As the constrictor ring 21 is forced onto thecollar 2, the material comprising the collar 2 flows partially into thechannels 26 to form a mechanical interlock.

It is preferred that the collar 2 be provided with an internal flange 27at its midportion, the flange having gradually tapered axial sides. Inassemblying a pair of constrictor rings onto the collar, the constrictorrings may be moved toward each other by suitable annular tools, notshown. It is preferred that such tools be provided with an internalflange or shoulder so that after the constrictor rings have been moved apredetermined distance onto the collar, that the ends of the collar areengaged and subjected to an axial compression force as well as theradial compression force produced by the constrictor rings. The taperedend of the tube 24 and a corresponding tapered end of a companion tubeor other member are initially pressed against the opposite sides of theinternal flange 27 so that on axial compression of the collar, intimatecontact is made between the tube and corresponding side of the flange27. Some buckling of the collar may occur between the flange 27 and theportion of the collar 2 constrained by the constrictor ring, asindicated by 28, assuring a sealing connection between the extremity ofthe tube and the internal flange as well as the series of sealingconnections provided in the regions of the channels 26.

Reference is directed to FIGS. 11, 12 and 13. The constricting collarand connector are particularly adapted for assemblying the components ofcondensers or heat exchangers. Condensers or heat exchangers are usuallyformed by a series of tubes, serially connected at their ends byU-tubes. More particularly, the U-tube 29 is provided with plain endswhich are received in bell ends 11 of a pair of tubes 1. In theconstruction illustrated, particularly with reference to FIG. 13, thebell ends of the tubes have an elongated taper rather than an abrupttaper, as indicated by the tapered shoulders 11c and 11d. Theconstrictor ring 30 may be similar to the constrictor ring 3, but isprovided at its leading end with a guide sleeve 31, having an internalbevel 5 at its leading end. Internally, the sleeve 31 is dimensioned tofit freely on the bell end 11. When the constrictor ring 30 is pressedonto the bell end, the relationship between the constrictor ring, bellend and extremity of the U-tube 29 is the same as previously described.

It will be noted that by reason of the presence of the U-tube, only aportion of the axial end of the constrictor ring is available forengagement by a pressing tool. By providing the sleeve 31, only thatportion of the constrictor ring exposed, as indicated in FIG. 11, needby engaged.

As it is desirable to place the bell end 11 under some compression, thetool, not shown, which engages the constrictor ring may also engage theend of the bell after the constrictor ring has been pressed apredetermined distance thereon. An opposing force may be exerted by atool fitting the tapered external shoulder 11d or the tube may beelsewhere held. The purpose being to apply the desired longitudinalcompression of the bell so as to obtain firm contact between theextremity of the U-tube and the internal shoulder 11c. In accomplishingthis, some buckling or expansion will occur in the region 32.

Reference is now made to FIG. 14. The construction shown particularly inFIG. 13 is also adapted to a connector involving a collar 2 and plainend tubes 1. In this case, the collar 2 is provided with an internalflange 27, similar to that shown in FIG. 10, and the constrictor ringsmay be similar to the constrictor ring 30; that is, provided withsleeves 31. However, a constrictor ring 3 may be used. As previouslydescribed, after the constrictor rings have been moved a predetermineddistance onto the collar, the collar is subjected to axial compressionto the extent that buckling 33 occurs at each side of the regionprovided with the internal flange 27.

If desired, the constrictor rings may be provided with the internalflange 23, as shown in FIG. 9.

It should be observed that with particular regard to the bell and tubeconstruction of FIGS. 5 and 6 that, when the coupling is completed, theportion of the bell 11 between the shoulder 11a and the region 10 aswell as the corresponding portion of the inner tube are under elasticstrain and that the force may be such as to deform the end of the tubeinto sealing engagement with the shoulder 11a.

With most suitable materials, plastic deformation is minimal and thereis an elastic balance between the tube, collar and constrictor ringwhich tends to increase the reliability of the coupling. Also, becausethe constrictor ring is under hoop tension, preferably close to itsyield limit, the coupling may be separated by cutting a notch in theconstrictor ring to cause it to break or snap and permit the collar andtube or tubes to be separated.

The present embodiments of this invention are to be considered in allrespects as illustrative and not restrictive.

I claim:
 1. The method of forming a permanently sealed joint between acircumferentially continuous normally cylindrical tubular outer memberand a circumferentially continuous normally cylindrical inner member,both of which members are of a ductile material having metal-likecharacteristics whereby they are capable of at least some resilientrecovery after being held deformed, comprising the steps of:a. applyinga radial force to one of said members throughout a first relativelynarrow circumferential zone at one axial end thereof and moving saidzone axially with respect to both of said members from the axial end ofsaid one member; b. applying successively greater radial forcesthroughout successive relatively narrow circumferential zones of bothmembers and moving said successive zones of both members axiallysimultaneously with the first zone in following relation thereto untilthe forces in a final zone are sufficient to deflect and plasticallydeform both said members radially to produce resilient sealing contacttherebetween throughout said final zone; c. continuing axial movement ofsaid zones until said final zone is spaced inwardly of the axial end ofsaid one member; and d. then stopping movement of said zones andrelieving at least said one member of all radial forces in a regionrearwardly of said final zone to permit said one member to resilientlyrecover at least in part, toward its original dimension and therebyprevent reverse movement of said zones.
 2. A method as defined in claim1, wherein:a. said one member is the outer tubular member; b. and saidradial force is applied radially inward thereon.
 3. The method utilizinga tapered deforming ring, for forming a permanently sealed joint betweena first and a second member having telescopable circular portions formedof ductile material capable of at least some resilient recovery afterbeing held in a deformed condition; the first member having an axial endaccessible to the deforming ring, said method characterized by:a. movingthe deforming ring axially to engage the axial end of said first memberand effect progressively increasing plastic deformation of said firstmember in a radial direction to cause axially progressive correspondingplastic deformation of the second member thereby to produce a resilientsealing zone between the members movable with movement of the deformingring; b. and continuing movement of the deforming ring and sealing zoneuntil a region of said first member clears the deforming ring to permitresilient recovery of said region of the first member toward itsoriginal dimension thereby to lock said deflector ring against reversemovement.
 4. A method as defined in claim 3, wherein:a. the first memberis disposed externally of the second member; b. the deforming ringcompresses the members radially inward; c. and said region recovers in aradially outward direction.
 5. A method as defined in claim 3,wherein:a. movement of the deforming ring is continued to effect plasticdeformation of the first member in at least two areas and form with thesecond member a corresponding number of sealing zones.
 6. A method asdefined in claim 5, wherein:a. said first member is permitted to effectresilient recovery in at least two regions.